Plastic tank structure

ABSTRACT

A PLASTIC TANK STRUCTURE COMPRISING A PLURALITY OF VERTICAL TUBULAR MEMBERS. THE TUBULAR MEMBERS CAN BE HOLLOW PLASTIC TUBES WHICH ARE PREFERABLY PLACED AROUND THE CIRCUMFERENCE OF A CIRCLE. EACH TUBE IS PLACED VERTICALLY ADJACENT ANOTHER TUBE AND A CURABLE ELASTOMERIC SEALANT IS IMPOSED BETWEEN THE WALLS OF ADJACENT TUBES. THE PLASTIC TUBES ARE ATTACHED TOGETHER BY JOINING MEANS, SUCH A BOLTS. THE BOTTOM END OF EACH TUBE IS FIRMLY EMBEDDED IN A BASE SUCH AS CONCRETE. THE ENCLOSURE FORMED BY THE PERIMETER OF VERTICAL PLASTIC TUBES IS CAPABLE OF STORING LIQUIDS OR SOLIDS. IT IS PARTICULARLY USEFUL FOR OIL STORAGE.

Oct. 5, 1971 CRANDAL 3,609,930

PLASTIC TANK STRUCTURE Original Filed Oct. 13, 196'? ,zfwsMroe 0m .L.QAMPAA,

//rs flrrmag s- United States Patent 3,609,930 PLASTIC TANK STRUCTUREEdwin L. Crandal, 435 Via Lido Soud, Newport Beach, Calif. 92660 FiledFeb. 24, 1970, Ser. No. 13,841 Int. Cl. E04b 1/56; E04c 1/16; E04b 7/02US. Cl. 52-245 8 Claims ABSTRACT OF THE DISCLOSURE A plastic tankstructure comprising a plurality of vertical tubular members. Thetubular members can be hollow plastic tubes which are preferably placedaround the circumference of a circle. Each tube is placed verticallyadjacent another tube and a curable elastomeric sealant is imposedbetween the walls of adjacent tubes. The plastic tubes are attachedtogether by joining means, such a bolts. The bottom end of each tube isfirmly embedded in a base such as concrete. The enclosure formed by theperimeter of vertical plastic tubes is capable of storing liquids orsolids. It is particularly useful for oil storage.

BACKGROUND OF THE INVENTION (1) Field of the invention This inventionrelates to plastic tank structures. In particular, this inventionrelates to oil storagetanks having vertical plastic tubular wallsegments.

(2) Description of the prior art The problem of supplying large diameterstorage tanks (i.e., 150 feet diameter) for storing oil or other liquidshas been only partially solved by the prior art structures which are inthe form of silos. The prior art structures are generally made ofconcrete or other ceramic elements. In some instances, hollow metallicbuilding elements have been used which are then joined together andreinforced by filling them with concrete. Another approach has been tosupply hollow ceramic building elements which interlock with adjoiningelements to form a unitary structure.

everal such structures are joined on vertically extending joint surfacesso that by utilizing a number of such units a vertically extending wallis formed. The problem wi.h these prior art structures is that they areextremely expensive to fabricate, and are also very bulky and heavy.Furthermore, maintenance problems are severe in such structures becauseof corrosion, if metallic sections are utilized or because if onesection of a ceramic unit is damaged it is extremely difficult torepair. It is virtually impossible to construct sections of prior artsilos at locations removed from the building site, because of the natureof the building blocks used and the fact that they have to be cementedtogether.

SUMMARY OF THE INVENTION In one of its broadest aspects the presentinvention encompasses a tank structure comprising a plurality ofvertical tubular members having upper and lower ends. The tubularmembers are placed vertically adjacent one another and are joined byjoining means. The tubular members are placed on the perimeter of anydesired geometrical area thereby forming a wall around the perimeter andcreating an enclosure Within the walls which enclosure is adapted tostore liquids or solids. The lower end of the vertical tubular membersare firmly embedded in a base material which forms the bottom of thestructure.

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The presently invented structure has several advantages over prior artstructures. It is apparent that plastic tubular members or tubes ofother material having a corrosion resistant coating or overwrap areresistant to abrasive forces and to corrosion from any liquids storedinside the tank. Furthermore, sections of a large tank, of say feetdiameter can be prefabricated away from the site of the tank becauselarge wall section can be constructed by bolting individual tubestogether. Since these tubes are lightweight it is possible to carrysections of the structure to the site where they can all be joinedtogether, preferably around the circumference of the circle to form acircular tank structure. Furthermore, such a tank is particularlyresistant to seismic disturbances because of the resilience of the thinwalled tubular members. If one section of such a tank becomes damaged,it is a relatively simple task to replace that section with anotherprefabricated section which has already been prepared and shipped to thesite.

Accordingly, it is a primary object of the present invention to providea container for the storage of solids or liquids having walls comprisingthin walled tubular members set into a base.

It is another object of the present invention to provide a plastic tankstructure which has a wall comprising plastic vertical tubular membersset around the circumference of the circle and whose lower ends are setin a concrete base.

Yet another object of the present invention is to provide a tankstructure which has a wall comprising metallic vertical tubular membershaving an overwrap of corrosion resistant reinforced plastic.

The novel features which are believed to be characteristic of theinvention, both as to its organization and method of operation, togetherwith further objects and advantages thereof will be better understoodfrom the following description considered in connection with theaccompanying drawing in which a presently preferred embodiment of theinvention is illustrated by way of example. It is to be expresslyunderstood, however, that the drawing is for the purpose of illustrationand description only, and is not intended as a definition of the limitsof the invention.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a front elevation of theinvented tank structure.

FIG. 2 is a plan view of several of the tubular members and theirjoining means.

FIG. 3 is a partially sectioned perspective of a tubular member and itsjoining means.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invented plastic tankstructure has been found particularly advantageous for the storage ofoil and will accordingly be described in connection with such use.

With reference now to FIG. 1 a plastic tank structure 10 comprisesvertical tubular members 12 which can be set on the circumference of acircle. It is of course within the scope of the invention to set thetubular members on the perimeter of any geometrical area therebyforming. an enclosure of the desired configuration. It is, however,highly advantageous for the storage of oil to set the tubular members onthe circumference of a circle. Typically, the diameter D of such astructure can be from about 60 feet to about 150 feet. The tubularmembers can conveniently be 20 feet long and 40 inches inside diameter,

and can be about 0.10 inch minimum thickness. In the preferredembodiment of the invention the tubular members are set into a concretebase which forms the fioor of the plastic structure.

The tubular members 12. are preferably of plastic. They must be of amaterial that is impervious to the contents of the tank structure. Inthis case they must be impervious to hydrocarbon oil and must havesufficient mechanical strength to oppose the forces put upon them byfull tanks of liquid or of seismic forces that may occur. In a 20 foottank containing water the pressure at the base of the tank will beapproximately 8 psi. One preferred method of fabricating such tubularmembers is by the filament winding process wherein a glass cloth isimpregnated with an elastomeric polyurethane or other thermosettingrain. Several layers of such glass cloth are overwrapped on a mandrel.The pipe thus formed is then cured and removed from the mandrel leavingthe hollow tubular member. The polyurethane resin used comprises apolyhydroxide compound and an isocyanate prepolymer used in suflicientquantities to effect a cure of the resin and to make it tough andresilient, yet having sufficient rigidity to withstand the mechanicalforce requirements of the structure. Such filament wound tubes have theadvantage of being lightweight and corrosion resistant and also havehigh tensile strength and can resist high bending moments. Alternativelythe tubular member can comprise a tube of extruded plastic such aspolyvinyl chloride which is then reinforced by an overwrap reinforcinglayer of lfibre glass impregnated with any particular resin which canthen be cured; or if the extruded plastic that is used meets amechanical strength requirement and has the chemical corrosionresistance required, no overwrap need be applied. Finally, thin gagesteel or other metal tubes, straight walled or corrugated, may be usedwhich can then be overwrapped with a reinforcing layer of resinimpregnated fibre glass.

Between each tube and the adjacent tube is placed a layer of sealant 14.This sealant can be made of any resilient material that is nonreactivewith the contents of the plastic tank structure. In this particular casethe sealant material must be nonreactive with hydrocarbon oils. One suchtough resilient material that may be used as a sealant is a polyurethaneelastomer comprising a polyhydroxide compound and a polyisocyanateprepolymer material mixed in sufiicient quantities to promote cure ofthe sealant material. This sealant serves the function of caulking thespaces between the tubular members to prevent any liquid inside the tankfrom leaking out. It also serves the function of forming a bond betweenadjacent tubes thereby holding them together, to resist shear forces dueto seismic or other loads. In addition to the sealant which bonds thetubes together, the tubes are held together by a series of bolts 16, 16aand 16b.

Referring now to FIGS. 2 and 3 there is shown a means by which tubularmembers 12 are joined to one another. Inside the hollow tubular membersand running vertically the whole length of them, there are bars ofmaterial 18 and 18a. These bars can conveniently be of wood or of anyother material which has sufiicient strength to resist warping when thebolts joining one tube to the next tube are tightened. The wooden bars18 and 18a are placed at opposite sides of the inside of the tubularmember and holes are drilled therethrough to allow bolts to be insertedthrough the wall of one tube and through the wall of an adjacent tubeand through the wooden bar in the adjacent tube. Alternatively steelwashers contoured to the curvature of the tube can be used inconjunction with fastening bolts. Such bolts can be spaced at variouspositions along the vertical axis of the wooden bars. The bolts canconveniently be positioned at three points equally spaced along thelength of the tube thus bolts 16, 16a, 16b join one tubular member tothe adjacent member. To meet loading requirement 4 inch bolts can beused spaced at equal distance throughout the length of the tube. For

.4 some applications this spacing will be about '6 inches and for otherapplications if high tensile bolts are used, the spacing can be greater.Between the two tubes is a layer 14 of sealant material as previouslydescribed. When the bolts are tightened, the wooden bars allow a largetorque force to be applied to the bolts without warping and withoutdamaging the walls of the tubes themselves. Thus the tubes are not onlyjoined by the adhesive forces of sealant 14, but also by the bolts whichcan be tightened to any desired degree. The whole structure is resistantto seismic or other mechanical forces which would tend to force apartthe tubular members. In addition reinforcing plates can be attached tothe base of the tank and to the concrete base to resist forces thatwould tend to overturn the tank. If it is desired to stabilize thesetubular members against buckling or other mechanical forces it ispossible to fill them with the same fluid that is in the tank. This hasthe effect of counteracting the compressive forces on the wall of thetubing.

The tubular members can be set around the circumference of a circle andtheir lower ends embedded into a base material to a predetermined depthwhich will promote stability of the structure. The base material canconveniently be concrete which is impervious to oil and other liquids.The tubular members could also be set into the ground which can thenhave concrete or other material impervious to liquids placed over it.

It is apparent from the foregoing description that the plastic tankstructure which is the subject of the present invention is advantageousin that it provides a corrosion resistant and lightweight structure forthe storage of oil or other liquid or solid materials. Another advantageof the present invention is that it can be constructed in sections andeasily transported to the proposed building site. Furthermore, if anyparticular segment of the wall of such a structure is damaged, thedamaged tubular members can easily be disconnected and replaced by newmembers. Another advantage is that the high strength of these plastictubes is such that they resist bending moments caused by seismic orother loading forces. Finally, the whole structure is relativelyinexpensive to construct when compared to the prior art ceramic siloswhich require cementing and other large expenditures of labor.

I claim:

1. A wall for a tank structure comprising:

a plurality of elongated tubular members;

a plurality of bars, at least two of which are disposed on the inside ofeach of said plurality of tubular members and which extend along thelength of said tubular members;

joining means, for rigidly coupling one of said bars in said tubularmembers with one of said bars in another of said tubular members therebyjoining two of said tubular members between said bars, said joiningmeans coupling all of said bars to form a continuous wall of saidtubular members.

2. The structure defined in claim 1 wherein said joining means comprisesbolt means disposed through said bars and said tubular members.

3. The structure defined in claim 2 wherein a sealant is disposed alongthe outside length of said tubular members adjacent to said plurality ofbars, for sealing said tubular members to one another.

4. The structure defined in claim 3 wherein said sealant comprises anelongated member of resilient material.

5. The structure defined in claim 3 wherein said sealant is a curableelastomeric resin.

6. The structure defined in claim 5 wherein sealant is a curableelastomeric polyurethane resin.

7. The structure defined in claim 1 wherein tubular members are made ofresin impregnated fibers.

said

said glass 8. The structure defined in claim 1 wherein said tubularmembers are made of extruded plastic having a resin impregnated glasstape overwrap.

References Cited UNITED STATES PATENTS Dungan 25624 Parton 52-169 Fieroh6134 Eames 52-245 X 6 2,815,656 12/1957 Klein et a1. 52293 X 3,337,9998/1967 Prus 52306 X 3,363,800 1/1968 Anderson 22083 3,383,004 5/1968Closner 2205 A PRICE C. FAW, IR., Primary Examiner US. Cl. X.R.

